Trencher or excavator? For pipeline distribution, power, water, sewer, gas and underdrain installations, as well as other heavy-duty trenching applications, both machines can do the work, yet excavators continue to be more prevalently used. But, this seems to be largely due to tradition. In fact, many contractors will tell you that they still install product with an excavator because that’s the way they’ve always done it.
But when it comes to productivity and efficiency when installing utilities, a trencher can be a better solution than an excavator.
Why? According to Barry Scieszinski and Gregg Van Roekel, Vermeer applications specialists for specialty excavation products, it’s because trenchers offer production efficiencies and will produce a cleaner trench cut to specification.
“When you think about what you’re doing — digging a ditch from Point A to Point B,” said Scieszinski, “both machines are designed to cut through and remove rocks or soils from the ground. But an excavator has to set up, dip, pull, swing, dump and repeat to do the job, and those repeated cycles take time. A trencher can remove the same rocks and soils in one continuous movement, which means that trenchers get you from Point A to Point B as quickly as possible. In many scenarios, a trencher can work three to four times faster than an excavator.”
Scieszinski added, “When the digging is done, even with your best excavator operators, what does the ditch look like? An excavator ditch will be wider at the top than it is at the bottom so you have a lot more backfill and it’s harder to compact when you backfill. With a trencher, the ditch will be clean with straight sidewalls and a flat bottom.”
Van Roekel concurred, “The goal on installation projects is to get in there, get the job done as efficiently and as cost-effectively as you can, and then get out so you can do the next job. With a trencher, you may be able to get more done more efficiently — it can be the fastest way to put product in the ground.”
Precise, quality cuts
When it comes to digging a quality trench, a trencher is superior to an excavator. For example, mentioned Van Roekel, when properly using a Vermeer track trencher, trenches will have flat, on-grade bottoms. “The trencher cuts exactly to its sizing,” said Van Roekel. “When properly sized, it only excavates the material that’s necessary, it produces an even trench all the way up to the top, and the spoil can be used as backfill in many cases, if not all.”
A trench dug with an excavator may not have a flat and even bottom, depending on the experience of the operator. For example, there can be a ripple at the bottom of the trench and uneven walls from overdigging. And, if a hammer attachment is used, the trench could be trapezoidal in shape from an operator starting with a narrow point and then digging wider with a bucket to get deeper. Not only is the crew excavating more material than necessary in that situation, but more backfill may be needed to get the trench to the required specification.
“An uneven bottom results in the need for more bedding, which may add to the cost of the project,” added Van Roekel.
Scieszinski agreed, “Trenches created by a Vermeer track trencher will have straight walls with specific dimensions. Due to the precise cutting of the trench, only the amount of spoil that is needed will be removed. A trench dug with an excavator can have jagged, uneven, irregular walls. More material is removed from the trench by an excavator than is necessary, adding to labor time and costs.”
Because excavators create trenches with uneven walls and inconsistent depths, once dug, these ditches may resist compaction and increase surface patching costs, more due to wider openings and irregular trench edges. As the surrounding structure settles, surface sinking may occur. These conditions can add substantial cost to a project.
“Trenches made by Vermeer trenchers will have flat bottoms and vertical walls, which means the refill will compact tightly,” said Van Roekel. “And with optional tilt tracks, a Vermeer trencher can keep a vertical trench wall automatically, even while trenching on a 5° slope. These features will help reduce the chances of the walls breaking up and eliminate someone constantly checking depth.”
Van Roekel added that a Vermeer trencher also boasts good visibility to follow the proposed trench plan. Operators may choose to lay out a string line or follow a land mark to trench on the correct line.
Doing more in less time
Part of a trencher’s productivity is its ability to efficiently cut a trench and produce more suitable backfill in a single pass. For example, a trencher can deposit spoil on either side of the
trench. Once the product is installed, a crew can follow behind with a dozer and push the material into the trench as backfill.
An excavator, however, often produces big chunks of material not suitable for immediate reuse. Suitable backfill often has to be hauled in, adding to the time and cost of a job. It’s an even bigger issue in rock. That material is hauled away, processed by a crusher, and then hauled back to the jobsite to serve as backfill. In other words, a contractor is handling that material three times using that method.
“It can be a huge cost to a contractor to handle backfill that way,” said Scieszinski. “On some jobs it can be more expensive than the cutting of the actual trench.”
As an example of the time and cost savings: A track trencher really excels in rocky conditions with its ability to efficiently cut rock of approximately 20 000 pounds per square inch (137.9 MPa) and lower. An excavator bucket, however, often cannot pierce rock of that specification. That means a contractor has to bring in a hammer attachment to break up the ground. Then a crew has to swap out that hammer with a bucket to dig the trench. Sometimes a contractor will have a separate machine to break the rock and another to dig the trench. Either way, that’s extra time and equipment on the jobsite.
“In those conditions, you can watch an excavator, and it might move 20 ft (6.1 m) an hour,” said Van Roekel. “In the same conditions, a trencher may have dug 500 ft (152.3 m) in an hour.”
Built hard nosed to power through soft soils to abrasive rock, Vermeer trenchers can be productive in a variety of soil types because these machines are purpose built for the pipeline market. They’re equipped with the TEC® Plus electronic control system, which adjusts the machine for straight tracking and provides real-time performance data and troubleshooting capabilities. “The TEC system can make training a new operator on a Vermeer trencher easier to teach than the excavator operator,” said Scieszinski. “With few hours of training, most Vermeer trencher operators can become very productive.”
He added, “And, because of this common control system among different models of trenchers, if you operate one of our track trenchers, you can quickly learn to run any of the similarly equipped Vermeer track trenchers.” Scieszinski noted that because excavators do not have TEC systems, operators may require more training and numerous hours of seat time to become productive.
Adding to their productivity, with trenchers, there are no heads to change — an operator can put the boom in the ground and go. But, with an excavator, an operator may need a hoe ram to break up rock then a bucket to scoop it out. “While changing heads may be a simple job, it adds to the time and labor costs of a job,” said Van Roekel.
Trenchers can also be more economical to transport, mentioned Scieszinski. For example, Vermeer trenchers feature a split cab which allows the machine width to be decreased for transport. “Thanks to the split cab, Vermeer trenchers can be transported without over-width permits,” he added. “Excavators do not feature split cabs and have a wider transport width than comparable Vermeer trenchers and may require an over-width permit.”
Because pipelines are such an important part of the world’s utility infrastructure, and while both machines have their roles on a jobsite, it is important to know the advantages of trenching versus excavating before starting your next pipeline project. “The trencher cuts a cleaner trench, cuts to grade, produces reusable spoil and can be faster,” Scieszinski concluded. Van Roekel finished, “As long as a contractor is in cuttable rock, a track trencher is generally going to outproduce an excavator.”
Vermeer Corporation reserves the right to make changes in engineering, design and specifications; add improvements; or discontinue manufacturing at any time without notice or obligation. Equipment shown is for illustrative purposes only and may display optional accessories or components specific to their global region. Please contact your local Vermeer dealer for more information on machine specifications. Vermeer, the Vermeer logo and TEC are trademarks of Vermeer Manufacturing Company in the US and/or other countries.
Read the article online at: https://www.worldpipelines.com/special-reports/01072022/know-the-advantages-of-trenching-versus-excavating/
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